Chapter 13. Memory, Learning, and Development
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By Michelle Roberts Health editor, BBC News online An increasingly warped sense of humour could be an early warning sign of impending dementia, say UK experts. The University College London study involved patients with frontotemporal dementia, with the results appearing in the Journal of Alzheimer's Disease. Questionnaires from the friends and family of the 48 patients revealed many had noticed a change in humour years before the dementia had been diagnosed. This included laughing inappropriately at tragic events. Experts say more studies are now needed to understand how and when changes in humour could act as a red flag for dementia. There are many different types of dementia and frontotemporal dementia is one of the rarer ones. The area of the brain it affects is involved with personality and behaviour, and people who develop this form of dementia can lose their inhibition, become more impulsive and struggle with social situations. Dr Camilla Clark and colleagues recruited 48 patients from their dementia clinic at University College London. And they asked the friends or relatives of the patients to rate their loved one's liking for different kinds of comedy - slapstick comedy such as Mr Bean, satirical comedy such as Yes, Minister or absurdist comedy such as Monty Python - as well as any examples of inappropriate humour. Nearly all of the respondents said, with hindsight, that they had noticed a shift in the nine years before the dementia had been diagnosed. Many of the patients had developed a dark sense of humour - for example, laughing at tragic events in the news or in their personal lives. The dementia patients also tended to prefer slapstick to satirical humour, when compared with 21 healthy people of a similar age. © 2015 BBC.
Link ID: 21617 - Posted: 11.10.2015
by Laura Sanders Babies’ minds are mysterious. Thoughts might be totally different in a brain that lacks words, and sensations might feel alien in a body so new. Are babies’ perceptions like ours, or are they completely different? Even if babies could talk, words would surely fail to convey what it’s like to experience, oh, every single thing for the first time. A recent paper offers a sliver of insight into young babies’ inner lives. The study, published October 19 in Current Biology, finds an example in which 4-month-old babies are happily oblivious to the external world. The research focuses on a perceptual trick that suckers adults and 6-month-old babies alike. When the hands are crossed, people often mistake which hand feels a touch. Let’s say your left hand (now crossed over to the right side of your body) gets a tickle. Your eyes would see a hand on the right side of your body get touched — a place usually claimed by your right hand, but now occupied by your left. Those mismatches between sight, touch and expectation can thwart you from quickly and correctly saying which hand was touched. Here’s the twist: 4-month-old babies don’t fall for this trick, Andrew Bremner of Goldsmiths, University of London and his colleagues found. In the experiment, a researcher would hold infants’ legs in either a crossed position or straight, while one of two remote-controlled buzzers taped to their feet tickled one foot. The researchers then watched which foot or leg wiggled as a result. If the buzzed foot moved, that meant that the baby got it right. © Society for Science & the Public 2000 - 2015.
By Erika Beras From the backseat of a cab, the moves a driver makes may at times seem, let’s say, daring. In fact, cabbies may actually be better, more agile drivers than the rest of us. Because they know their streets so well. Previous research found that the hippocampus in the brain of a typical cab driver is enlarged. That’s the part of the brain used in navigation. But now a study confirms that learning detailed navigation information does indeed cause that part of the brain to grow. The findings are in the journal NeuroImage. Researchers had young adults who were not regular gamers play a driving simulation game. Some practiced maneuvering the same route 20 times, while other players were confronted with 20 different routes. The participants’ brains were scanned before they performed the simulated driving and again after. Researchers found that subjects who kept repeating the same route increased their speed more than those driving multiple routes. The single-route drivers were also much better able to put in order a sequence of random pictures taken along the way and to draw a map of the route. The investigators also found increases in the single-route drivers in the functional connectivity between the hippocampus and other parts of the brain involved with navigation. And the amount of change was directly related to the amount of improvement each participant displayed. © 2015 Scientific American
Keyword: Learning & Memory
Link ID: 21612 - Posted: 11.07.2015
Laura Sanders Specialized cells that make up the brain’s GPS system have an expanding job description. In addition to mapping locations, these cells can keep track of distance and time, too, scientists report in the Nov. 4 Neuron. Those specialized cells, called grid cells, were thought to have a very specific job, says neuroscientist Loren Frank of the University of California, San Francisco. But, he says, the new study says, “not so fast, everybody.” These cells’ ability to detect time and distance is unexpected. “And I think it’s important,” Frank says. The growing to-do list of grid cells shows that the brain’s navigational system is surprisingly flexible. The discovery of grid cells, found in a part of the brain called the entorhinal cortex, was recognized with the Nobel Prize last year (SN Online: 10/6/14). These brain cells fire off regular signals as animals move around in space, partially forming an internal map of the environment. Neuroscientist Howard Eichenbaum of Boston University and colleagues wondered what those cells do when an animal stays put. By training rats to run on a treadmill, the researchers had a way to study grid cells as time and distance marched forward, but location remained the same. Unlike recently discovered “speed cells” (SN: 8/8/15, p. 8), these grid cells don’t change their firing rates to correspond to changes in the rats’ swiftness, the researchers found. Instead, these cells stay tuned to distance or time, or both. © Society for Science & the Public 2000 - 2015.
Keyword: Learning & Memory
Link ID: 21606 - Posted: 11.05.2015
By DAVE ITZKOFF and BENEDICT CAREY For the first time in more than a year, the widow of the actor Robin Williams is speaking publicly about the circumstances that preceded Mr. Williams’s death, and sharing details about a disease he had when he died. Stories from Our Advertisers In interviews with People magazine and with ABC News, the widow, Susan Schneider Williams, laid the blame for her husband’s suicide in 2014 not on depression but on diffuse Lewy body dementia. “It was not depression that killed Robin,” Mrs. Williams said in the People magazine interview. “Depression was one of let’s call it 50 symptoms and it was a small one.” She added: “This was a very unique case and I pray to God that it will shed some light on Lewy bodies for the millions of people and their loved ones who are suffering with it. Because we didn’t know. He didn’t know.” Parts of an interview with Mrs. Williams were shown Tuesday on ABC’s “Good Morning America,” with further segments scheduled for that evening on the network’s “World News Tonight” and “Nightline” programs, and Friday on its morning talk show “The View.” Robin Williams was one of the most explosively, exhaustingly, prodigiously verbal comedians who ever lived, says film critic A. O. Scott. And the only thing faster than Williams’s mouth was his mind. By Adam Freelander on Publish Date August 12, 2014. Photo by ABC, via Associated Press. Watch in Times Video » Mr. Williams, the stand-up comic and star of “Mork & Mindy,” “Good Morning, Vietnam,” “Good Will Hunting” (for which he won an Oscar) and “Dead Poets Society,” killed himself on Aug. 11, 2014, in the home he shared with Mrs. Williams in Tiburon, Calif. He was 63. © 2015 The New York Times Company
Sara Reardon Military-service members can suffer brain injury and memory loss when exposed to explosions in enclosed spaces, even if they do not sustain overt physical injury. A strategy designed to improve memory by delivering brain stimulation through implanted electrodes is undergoing trials in humans. The US military, which is funding the research, hopes that the approach might help many of the thousands of soldiers who have developed deficits to their long-term memory as a result of head trauma. At the Society for Neuroscience meeting in Chicago, Illinois, on 17–21 October, two teams funded by the Defense Advanced Research Projects Agency presented evidence that such implanted devices can improve a person’s ability to retain memories. By mimicking the electrical patterns that create and store memories, the researchers found that gaps caused by brain injury can be bridged. The findings raise hopes that a ‘neuroprosthetic’ that automatically enhances flagging memory could aid not only brain-injured soldiers, but also people who have had strokes — or even those who have lost some power of recall through normal ageing. Because of the risks associated with surgically placing devices in the brain, both groups are studying people with epilepsy who already have implanted electrodes. The researchers can use these electrodes both to record brain activity and to stimulate specific groups of neurons. Although the ultimate goal is to treat traumatic brain injury, these people might benefit as well, says biological engineer Theodore Berger at the University of Southern California (USC) in Los Angeles. That is because repeated seizures can destroy the brain tissue needed for long-term-memory formation. © 2015 Nature Publishing Group
By Michelle Roberts Health editor, BBC News online Brain training - playing online games that give memory and reasoning skills a workout - is beneficial for older people, a large-scale study has concluded. Researchers at King's College London found the mental exercises kept minds sharp and helped people with everyday skills such as shopping and cooking. Nearly 7,000 people aged 50 and over signed up for the six-month experiment, launched by BBC TV's Bang Goes The Theory. Longer studies are now beginning. The volunteers were recruited from the general population by a partnership between the BBC, the Alzheimer's Society and the Medical Research Council. As far as the investigators were aware, none had any problems with memory or cognition when they signed up to the experiment. Some of the volunteers were encouraged to play online brain training games for 10 minutes at a time, as often as they wished. The others - the control group - were asked to do simple internet searches. The researchers tested the subjects on a series of medically recognised cognitive tests at baseline and then again at three months and six months to see if there was any detectable difference between the groups. The researchers found after six months, those who played "brain training" games for reasoning and problem-solving kept their broader cognitive skills better than those who did not. The benefit appeared to kick in when people played the games at least five times a week. And people over 60 who played these games reported better scores for carrying out essential everyday tasks, the Journal of Post-acute and Long Term Care Medicine reports. © 2015 BBC
By Jennie Baird Last week’s news that Sesame Street was introducing the first autistic Muppet was met in my house with a resounding, “Huh?” “But there already is an autistic Muppet,” my high-functioning 14-year-old said. “Fozzie Bear.” I had never thought of Fozzie that way, but my son had a point. Fozzie is not good at taking social cues; he doesn’t read a room well and he tends to monologue and perseverate (to repeat himself long after the need has passed). He interprets figurative language as literal — remember that fork in the road in “The Muppet Movie?” He has a verbal tic he falls back on, “wokka-wokka.” And he hates to be separated from his hat for no obvious reason. I’ve tested this theory on friends and have seen the light bulb of recognition go off every time. Of course Fozzie has autism! One friend, a mother whose son is also on the spectrum even told me her family had the exact same conversation. Sesame Street hopes children will identify with their new character Julia, described as a “friend who has autism,” and appearing, for now, only in the book “We’re Amazing 1-2-3!” There is no question, the mere presence of Julia is a positive development. But she also introduces a rarely discussed complication of autism. Let’s call it the Fozzie Conundrum. I’m particularly sensitive to the Fozzie Conundrum now that my son attends regular honors classes in a regular public high school. Naturally sociable and charismatic — and with eight years of support and interventions from a team of terrific teachers and therapists at specialized schools — he can easily “pass” as a regular, funny, quirky teenager. © 2015 The New York Times Company
Link ID: 21590 - Posted: 11.02.2015
By Nicholas Bakalar Certain personality traits are often attributed to oldest, middle and youngest children. But a new study found that birth order itself had no effect on character, though it may slightly affect intelligence. Researchers analyzed three large ongoing collections of data including more than 20,000 people: a British study that follows the lives of people who were born in one particular week in 1958, a German study of private households started in 1984 and a continuing study of Americans born between 1980 and 1984. They searched for differences in extroversion, emotional stability, agreeableness, conscientiousness, self-reported intellect, IQ, imagination and openness to experience. They analyzed families with sisters and brothers, large and small age gaps and different numbers of siblings. They even looked to see if being a middle child correlated with any particular trait. But no matter how they spliced the data, they could find no association of birth order with any personality characteristic. The study, in Proceedings of the National Academy of Sciences, did find evidence that older children have a slight advantage in IQ scores, but the difference was apparent only in a large sample, with little significance for any individual. The lead author, Julia M. Rohrer, a graduate student at the University of Leipzig, said that birth order can have an effect — if your older brother bullied you, for example. “But these effects are highly idiosyncratic,” she said. “There is no such thing as a typical older, middle or younger sibling. It’s important to stop believing that you are the way you are because of birth order.” © 2015 The New York Times Company
A drug for Alzheimer’s seems to delay the point at which a person with the condition needs to be moved into a nursing home. Donepezil is usually given to people with moderate forms of the disease, but continuing to take the drug once the disease becomes more severe seems to prolong the period of time a person can remain in their own home. Previously, the drug was not thought to benefit people once they had developed more severe forms of Alzheimer’s. But a study that followed 295 people with moderate to severe Alzheimer’s disease found that those who continued to take donepezil were nearly half as likely to end up in a care home within the next year. “It could mean thousands of patients per year not going into care homes,” says Robert Howard of University College London, who led the study. His team found that those who continued to take donepezil had a 20 per cent chance of being moved into a care home within the first year of the trial, compared to 37 per cent in those who stopped taking the drug. However the effect didn’t last. The trial lasted for three years, and after the first year, those who taking donepezil were just as likely to be moved into a home than those who weren’t, suggesting that the drug does not have a longer-term effect on the care needs of those with Alzheimer’s. “For every six patients treated with donepezil for 12 months, you would prevent one moving into a nursing home,” says Howard. “It’s a modest effect, but it’s important if it’s your mother or your wife.” © Copyright Reed Business Information Ltd.
Link ID: 21577 - Posted: 10.28.2015
When we hear speech, electrical waves in our brain synchronise to the rhythm of the syllables, helping us to understand what’s being said. This happens when we listen to music too, and now we know some brains are better at syncing to the beat than others. Keith Doelling at New York University and his team recorded the brain waves of musicians and non-musicians while listening to music, and found that both groups synchronised two types of low-frequency brain waves, known as delta and theta, to the rhythm of the music. Synchronising our brain waves to music helps us decode it, says Doelling. The electrical waves collect the information from continuous music and break it into smaller chunks that we can process. But for particularly slow music, the non-musicians were less able to synchronise, with some volunteers saying they couldn’t keep track of these slower rhythms. Rather than natural talent, Doelling thinks musicians are more comfortable with slower tempos because of their musical training. As part of his own musical education, he remembers being taught to break down tempo into smaller subdivisions. He suggests that grouping shorter beats together in this way is what helps musicians to process slow music better. One theory is that musicians have heard and played much more music, allowing them to acquire “meta-knowledge”, such as a better understanding of how composers structure pieces. This could help them detect a broader range of tempos, says Usha Goswami of the University of Cambridge. © Copyright Reed Business Information Ltd.
By Jessica Schmerler Young brains are plastic, meaning their circuitry can be easily rewired to promote learning. By adulthood, however, the brain has lost much of its plasticity and can no longer readily recover lost function after, say, a stroke. Now scientists have successfully restored full youthful plasticity in adult mice by transplanting young neurons into their brain—curing their severe visual impairments in the process. In a groundbreaking study published in May in Neuron, a team of neuroscientists led by Sunil Gandhi of the University of California, Irvine, transplanted embryonic mouse stem cells into the brains of other mice. The cells were primed to become inhibitory neurons, which tamp down brain activity. Prior to this study, “it was widely doubted that the adult brain would allow these cells to disperse, integrate and reactivate plasticity,” says Melissa Davis, first author of the study. Scientists have been attempting such a feat for years, refining their methods along the way, and the Irvine team finally saw success: the cells were integrated in the brain and caused large-scale rewiring, restoring the high-level plasticity of early development. In visually impaired mice, the transplant allowed for the restoration of normal vision, as demonstrated by tests of visual nerve signals and a swimming maze test. The scientists have not yet tested the transplanting technique for other neurological disorders, but they believe the technique has potential for many conditions and injuries depending on how, exactly, the new neurons restore plasticity. It is not yet known whether the proliferation of the transplanted cells accounts for the restored plasticity or if the new cells trigger plasticity in existing neurons. If the latter, the treatment could spur the rewiring and healing of the brain following traumatic brain injury or stroke. © 2015 Scientific American
By GINA KOLATA Three diseases, leading killers of Americans, often involve long periods of decline before death. Two of them — heart disease and cancer — usually require expensive drugs, surgeries and hospitalizations. The third, dementia, has no effective treatments to slow its course. So when a group of researchers asked which of these diseases involved the greatest health care costs in the last five years of life, the answer they found might seem surprising. The most expensive, by far, was dementia. The study looked at patients on Medicare. The average total cost of care for a person with dementia over those five years was $287,038. For a patient who died of heart disease it was $175,136. For a cancer patient it was $173,383. Medicare paid almost the same amount for patients with each of those diseases — close to $100,000 — but dementia patients had many more expenses that were not covered. On average, the out-of-pocket cost for a patient with dementia was $61,522 — more than 80 percent higher than the cost for someone with heart disease or cancer. The reason is that dementia patients need caregivers to watch them, help with basic activities like eating, dressing and bathing, and provide constant supervision to make sure they do not wander off or harm themselves. None of those costs were covered by Medicare. For many families, the cost of caring for a dementia patient often “consumed almost their entire household wealth,” said Dr. Amy S. Kelley, a geriatrician at Icahn School of Medicine at Mt. Sinai in New York and the lead author of the paper published on Monday in the Annals of Internal Medicine. © 2015 The New York Times Company
Link ID: 21571 - Posted: 10.27.2015
By Dina Fine Maron Early-life exposure to anesthesia does not appear to lead to long-term cognitive problems, researchers announced today. New evidence from the first, randomized anesthesia trial in kids provides the strongest indication yet that exposing young children to anesthesia—at least for a brief time—will not saddle them with developmental deficits. The news comes just a couple of weeks after a medical advisory group reiterated its concerns about such exposures among children younger than four years. Previously, multiple animal and human studies have linked such exposure with cognitive impairment, but none of the information on humans came from a gold-standard, randomized study design that could help eliminate other reasons to explain such a connection. This is a “reassuring finding, but it is not the final answer,” says Dean Andropoulos, anesthesiologist in chief at Texas Children’s Hospital and an expert who was not involved in the work. The new study assesses only what happens to youngsters after a relatively brief bout with anesthetics, so it is possible that longer or repeated exposures to such chemicals may still cause neurodevelopmental issues. There may also be deficits in anesthesia-exposed children that are not measurable until later in life. The study followed more than 500 infants undergoing hernia repair across the U.S., Australia, the U.K., Canada, the Netherlands, New Zealand and Italy. The surgeries lasted an average of roughly an hour. About half of the children were randomly selected to be put under with general anesthesia, and the other half stayed awake during the surgery and received targeted anesthesic in a specific body region. The kids in the study were all younger than 60 weeks and were matched by where they had the surgery and whether they were born prematurely. © 2015 Scientific American
Richard A. Friedman YOU can increase the size of your muscles by pumping iron and improve your stamina with aerobic training. Can you get smarter by exercising — or altering — your brain? Stories from Our Advertisers This is hardly an idle question considering that cognitive decline is a nearly universal feature of aging. Starting at age 55, our hippocampus, a brain region critical to memory, shrinks 1 to 2 percent every year, to say nothing of the fact that one in nine people age 65 and older has Alzheimer’s disease. The number afflicted is expected to grow rapidly as the baby boom generation ages. Given these grim statistics, it’s no wonder that Americans are a captive market for anything, from supposed smart drugs and supplements to brain training, that promises to boost normal mental functioning or to stem its all-too-common decline. The very notion of cognitive enhancement is seductive and plausible. After all, the brain is capable of change and learning at all ages. Our brain has remarkable neuroplasticity; that is, it can remodel and change itself in response to various experiences and injuries. So can it be trained to enhance its own cognitive prowess? The multibillion-dollar brain training industry certainly thinks so and claims that you can increase your memory, attention and reasoning just by playing various mental games. In other words, use your brain in the right way and you’ll get smarter. A few years back, a joint study by BBC and Cambridge University neuroscientists put brain training to the test. Their question was this: Do brain gymnastics actually make you smarter, or do they just make you better at doing a specific task? For example, playing the math puzzle KenKen will obviously make you better at KenKen. But does the effect transfer to another task you haven’t practiced, like a crossword puzzle? © 2015 The New York Times Company
As we get older, most of us will experience some kind of brain degeneration. Typically, we lose the ability to make new neurons. Another problem is chronic, low-grade inflammation in the brain, which is implicated in many age-related brain disorders. To tackle both problems in one go, Ludwig Aigner at Paracelsus Medical University Salzburg in Austria and his colleagues targeted a set of receptors in the brain that, when activated, trigger inflammation. High numbers of these receptors are found in areas of the brain where neurons are born, suggesting they might also be involved in this process, too. A drug called montelukast (Singulair), regularly prescribed for asthma and allergic rhinitis, blocks these receptors, so Aigner and his colleagues tried it on young and old rats. The team used oral doses equivalent to those taken by people with asthma. The older animals were 20 months old – roughly equivalent to between 65 and 75 in human years. The younger rats were 4 months old – about 17 in human years. The animals were fed the drug daily for six weeks, while another set of young and old rats were left untreated. There were 20 young and 14 old rats in total. The rats took part in a range of learning and memory tests. One of these, for example, involved the rats being placed in a pool of water with a hidden escape platform. At the start of the study, untreated young rats learned to recognise landmarks and quickly find their way to the platform, while the untreated older animals struggled at the task. © Copyright Reed Business Information Ltd.
Claire Cain Miller Boys are falling behind. They graduate from high school and attend college at lower rates than girls and are more likely to get in trouble, which can hurt them when they enter the job market. This gender gap exists across the United States, but it is far bigger for poor people and for black people. As society becomes more unequal, it seems, it hurts boys more. New research from social scientists offers one explanation: Boys are more sensitive than girls to disadvantage. Any disadvantage, like growing up in poverty, in a bad neighborhood or without a father, takes more of a toll on boys than on their sisters. That realization could be a starting point for educators, parents and policy makers who are trying to figure out how to help boys — particularly those from black, Latino and immigrant families. “It’s something about family disadvantage itself,” said David Figlio, a Northwestern University economist and co-author of a new paper, presented publicly for the first time on Thursday. “Black people in America are more disadvantaged than white people in America, and if we were to reduce the disadvantage, we may see a reduction in the relative gender gap as well.” Marianne Bertrand, an economist at University of Chicago who with Jessica Pan has studied the gender gap, also found that boys fare worse than girls in disadvantaged homes, and are more responsive than girls to parental time and resources. “Their findings were very consistent: Families that invest more in children are protective for boys,” she said. The reasons that boys react more negatively to disadvantage are varied and hard to pinpoint. Even in utero, boys are more sensitive to extreme stress than girls, and tend to have more unruly temperaments. Society discourages boys from showing vulnerability. Low-income families are often led by single mothers, which has been found to affect boys differently than girls. © 2015 The New York Times Company
Elizabeth Blair The muppet Julia has not yet made her TV debut, but the wide-eyed little girl with a big smile is the star of her own "digital storybook" called "We're Amazing, 1,2,3." For over a year now, Sesame Street has been working with organizations such as Autism Speaks and Autism Self Advocacy to help reduce the stigma associated with autism spectrum disorder. As part of the campaign "See Amazing in All Children," the adorable muppet Abby Cadabby explains in one YouTube video, "Lots of kids have autism and that just means their brains work a little differently." Julia is not the first fictional media character with autism. But Michael Robb, Director of Research for Common Sense Media, an organization that rates and reviews media aimed at children, says Sesame Street's move is "pretty groundbreaking." "It can be difficult to start a conversation about children with disabilities. It's even harder when that difference isn't visible," he says. After looking through "We're Amazing, 1,2,3," Robb says the story could help children be more understanding of how Julia is different. "It's very real in terms of talking in simple language. It spells out these things in concrete ways that kids can understand. It shows ways she's just like other kids. It shows how making simple accommodations can help Julia." According to Dr. Jeanette Betancourt, Senior Vice President of U.S. Social Impact at Sesame Workshop, says Sesame Street producers are waiting to hear back from the autism community before introducing Julia to the show on TV. © 2015 npr
Link ID: 21557 - Posted: 10.24.2015
Alzheimer's disease can be detected decades before onset, using a virtual reality test, a study suggests. People aged 18 to 30 were asked to navigate through a virtual maze to test the function of certain brain cells. Those with a high genetic risk of Alzheimer's could be identified by their performance, according to German neuroscientists. The findings could help future research, diagnosis and treatment, they report in the journal Science. The scientists, led by Lukas Kunz of the German Centre for Neurodegenerative Diseases in Bonn, say the high risk group navigated the maze differently and had reduced functioning of a type of brain cell involved in spatial navigation. The findings could give an insight into why people with dementia can find navigating the world around them challenging, they say. "Our results could provide a new basic framework for preclinical research on Alzheimer's disease and may provide a neurocognitive explanation of spatial disorientation in Alzheimer's disease," they report in Science. Although genes play a role in dementia, their effects are complex with many unknowns. Dr Laura Phipps of Alzheimer's Research, said the latest study focused on healthy younger people at higher genetic risk of Alzheimer's, suggesting they may already show alterations in spatial navigation several decades before the disease could start. © 2015 BBC.
Link ID: 21555 - Posted: 10.23.2015
By Tara Parker-Pope Children who regularly use antibiotics gain weight faster than those who have never taken the drugs, according to new research that suggests childhood antibiotics may have a lasting effect on body weight well into adulthood. The study, published in the International Journal of Obesity, examined the electronic medical records of 163,820 children ages 3 to 18, counting antibiotic prescriptions, body weight and height. The records, which covered pediatric exams from 2001 through 2012, showed that one in five — over 30,000 children — had been prescribed antibiotics seven or more times. By the time those children reached age 15, they weighed, on average, about 3 pounds more than children who had received no antibiotics. While earlier studies have suggested a link between antibiotics and childhood weight gain, they typically have relied on a mother’s memories of her child’s antibiotic use. The new research is significant because it’s based on documented use of antibiotics in a child’s medical record. “Not only did antibiotics contribute to weight gain at all ages, but the contribution of antibiotics to weight gain gets stronger as you get older,” said Dr. Brian S. Schwartz, the first author and a professor in the department of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. Scientists have known for years that antibiotic use promotes weight gain in livestock, which is why large food producers include low doses of antibiotics in the diets of their animals. © 2015 The New York Times Company